Many semiconductor devices require that contact regions be formed that electrically couple one surface of the device to a sub-surface feature or structure such as a buried layer or underlying substrate. When the sub-surface regions are deep within the substrate or an epitaxial layer (e.g., greater than about 10 microns), making the contact regions can be a challenge. Typically, manufacturers use very high energy ion implantation techniques and/or deep diffusions to drive dopants deep enough to make contact to the sub-surface feature. Alternatively, manufacturers use double diffusion techniques where a first region is implanted into a substrate, an epitaxial layer is then deposited, and a second region is implanted into the epitaxial layer above the first region. The two regions are then diffused together.
Deep high energy ion implants can be prohibitively expensive, and are technically unfeasible in some cases. Additionally, deep diffused regions including double diffused regions can adversely affect the size of a semiconductor device because the diffused dopants move or diffuse in all directions. Further, contact resistance associated with deep diffused mono-silicon layers can be quite high, which detrimentally impacts device performance.
In addition, as semiconductor devices evolve to include additional functionality on smaller chips, existing manufacturing processes are not flexible enough to support the additional functionality without significant increases in costs.
Accordingly, a structure and method of forming the structure are needed that provide a contact to a sub-surface feature or features, and that address the problems set forth above as well as others. Additionally, it would be advantageous for the structure to be usable for multiple purposes to save on costs.